



class Solution
{
public:
  double findMedianSortedArrays(int A[], int m, int B[], int n)
  {
    int total = m + n;
    if (total & 0x1)
      return findKth(A, m, B, n, total / 2 + 1);
    else
      return (findKth(A, m, B, n, total / 2)
          + findKth(A, m, B, n, total / 2 + 1)) / 2;
  }
  double findKth(int a[], int m, int b[], int n, int k) {
    //always assume that m is equal or smaller than n
    if (m > n)
      return findKth(b, n, a, m, k);
    if (m == 0)
      return b[k - 1];
    if (k == 1)
      return min(a[0], b[0]);
    //divide k into two parts
    int pa = min(k / 2, m), pb = k - pa;
    if (a[pa - 1] < b[pb - 1])
      return findKth(a + pa, m - pa, b, n, k - pa);
    else if (a[pa - 1] > b[pb - 1])
      return findKth(a, m, b + pb, n - pb, k - pb);
    else
      return a[pa - 1];
  }
};



